Question

A patient is admitted to the hospital with dyspnea and COPD exacerbation. The orders from the physician include:

• Stat ABGs, chest x-ray, complete blood count, and electrolytes

• IV D5W/½ NS 1000 mL/8 hr

• Aminophylline IV loading dose of 5.6 mg/kg over 30 minutes followed by 0.5 mg/kg/hr continuous IV

• O₂ at 2 L/min per nasal cannula

• Albuterol respiratory treatments every 4h

• Chest physiotherapy every 4h

• Erythromycin 800 mg IV every 6h

• Bed rest

• Accurate intake/output

• High-calorie, protein-rich diet in six small meals daily

• Encourage PO fluids to 3 L/day

Identify the orders that require calculations.

Set up and solve each problem using dimensional analysis.

• Calculate mL/hr to set the IV pump.

• Calculate mL/hr to set the IV pump for the loading dose of aminophylline for a patient weighing 140 lb. Aminophylline supply: 100 mg/100 mL D5W.

• Calculate mL/hr to set the IV pump for the continuous dose of aminophylline for a patient weighing 140 lb. Aminophylline supply: 1 g/250 mL D5W.

• Calculate mL/hr to set the IV pump to infuse erythromycin 800 mg. Erythromycin supply: 1-g vial to be reconstituted with 20 mL sterile water and further diluted in 250 mL NS to infuse over 1 hr.

• Calculate the PO fluids in mL/shift.

Answer 1

1. Calculate mL/hr to set the IV pump.

Data given

  IV D5W/½ NS 1000 mL/8 hr

mL/hr to set the IV pump = 1000 mL/8 hr = 125 mL/hr

The answer is mL/hr to set the IV pump =125 mL/hr

2. Calculate mL/hr to set the IV pump for the loading dose of aminophylline for a patient weighing 140 lb. Aminophylline supply: 100 mg/100 mL D5W.

Data given

  Aminophylline IV loading dose = 5.6 mg/kg over 30 minutes

Weight of the patient = 140 lb = 64 kg

Aminophylline supply (Concentration) =100 mg/100 mL = 1 mg/mL

So, the Aminophylline IV loading dose required = 5.6 mg x 64 kg = 358.4 mg = 358 mg (Round value)

mL of Aminophylline required = (required dose / available dose)x availabe dose in mL

= (358 mg / 100mg) x 100 mL

= 358 mL

Formula for flow rate is

(Volume in mL x 60)/Time in min = mL / hr

mL/hr to set the IV pump for the loading dose of aminophylline = (358 mL x 60) x 30

= 716 mL/hr

The answer is - mL/hr to set the IV pump for the loading dose of aminophylline = 716 mL/hr

3. Calculate mL/hr to set the IV pump for the continuous dose of aminophylline for a patient weighing 140 lb. Aminophylline supply: 1 g/250 mL D5W.

Data given

Reuired dose =  0.5 mg/kg/hr

Weight of the patient= 140 lb = 64 kg

Aminophylline supply (concentration)= 1 g/250 mL=4 mg/mL

mL/hr to set the IV pump for the continuous dose of aminophylline = Required dose/concentration

=  0.5 mg/kg/hr / 4 mg/mL

= (0.5 mg x 64 kg/hr)/4 mg/mL

= 8 mL/hr

The answer is mL/hr to set the IV pump for the continuous dose of aminophylline =8 mL/hr

4. Calculate mL/hr to set the IV pump to infuse erythromycin 800 mg. Erythromycin supply: 1-g vial to be reconstituted with 20 mL sterile water and further diluted in 250 mL NS to infuse over 1 hr.

Desired dose or dose ordered = 800 mg

Available dose = 1 g = 1000 mg

Resconstituting in 20 mL sterile water. So Concentration = 20 mL

FORMULA FOR DOSE CALCULATION IS

Desired dose x quantity = dose to be given

Available dose

So, 800 mg x 20 mL = 16 mL

1000 mg

16 mL is further diluted in 250 mL NS. So

The total volume to be infused over 1 hr = 250+16 = 266 mL

The answer is mL/hr to set the IV pump to infuse erythromycin 800 mg over i hr is 266 mL

5. Calculate the PO fluids in mL/shift.

Total volume of fluid per day = 3 L = 3000 mL (1 liter = 1000 mL)

125 mL/ hr. so if we consider an 8 hr per shift ( AS IT IS NOT MENTIONED IN THE QUESTION).

The volume of oral intake per shift is

125 x 8 = 1000 mL